Diagnosing Brown Spots on Phalaenopsis Leaves: Scale or Fungus?

Two Likely Causes

Small brown spots on Phalaenopsis leaves could be:

Scale insects: Sucking pests resembling tiny turtle shells. Test by rubbing a spot with a cotton swab dipped in rubbing alcohol. If it comes off, it's scale.
Fungal infection: If spots don't rub off, suspect fungus.

Scale: Remove all visible insects with alcohol swabs. Repeat weekly for several weeks to catch hatchlings. Apply systemic insecticide (e.g., Bayer Advanced) for long-term control.
Fungus: Spray with orchid-safe fungicide over several weeks. Spots remain but spread stops.

Orchids: Encouraging Blooms on a Mature Phalaenopsis Orchid; Spots on Phalaenopsis Flower Petals: Natural Aging; Black Spots on New Orchid Growth: Fungal from Water on Leaves; Mealybugs on Orchid Leaves: Alcohol and Systemic Treatment; Multiple New Spikes on Phalaenopsis: Pinch or Let Grow?; Botrytis on Cymbidium Flowers: Prevention and Quick Action; Black Streaks on Orchid Leaves: Fungal vs. Bacterial Infection Management; Green Spots on White Orchid Flowers: Insect Damage, Not Fungus; Yellow Eggs on Orchid Bark & Leaf Sunburn: Diagnosis and Care; First Phalaenopsis: Diagnosing Black Leaf Spots—Sunburn vs. Fungus

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